Applicant claims, under 35 U.S.C. xc2xa7119, the benefit of priority of the filing date of Jan. 24, 1998 of a German patent application, copy attached, Serial Number 198 02 728.1, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
The present invention relates to a method for monitoring machine parameters in a numerical controller and to a circuit configuration for performing the method as generically defined by the preamble to claim 7.
From European Patent Disclosure EP 742 499 A2, a method for secure processing of safety-oriented process signals is known. In it, process signals are carried independently of one another to at least two likewise-independent computers, which thus form at least two monitoring channels. In the computers, the process signals are subjected to a separate, projectable input signal processing. In this operation, a crosswise data and result comparison takes place. The signals formed by the input signal processing are interpreted in the monitoring channels, and output signals that take the applicable process state into account are generated; a crosswise data and result comparison is performed between each two monitoring channels. Next, the output signals generated are subjected in the two computers to a separate, projectable output signal processing; once again, the computers perform a crosswise data and result comparison. Finally, with the secure output signals of the monitoring channels that have been obtained, safety-relevant parameters of the process are controlled redundantly.
This version has the disadvantage that process signals have to be ascertained independently of one another. If parameters are input by the user, for instance in an initializing phase, independent ascertainment is not possible.
From European Patent Disclosure EP 742 505 A2, a device for safety-oriented monitoring of a machine is known in which for redundant, processor-supported monitoring, predeterminable data and data about current status parameters of the monitoring can all be written in, stored and read out separately. For monitoring the axis states, the read-out data and the data of the corresponding transducers are delivered to channel comparators in the two redundant channels, and if there is no match of the paired data, predeterminable error reactions are tripped by the channel comparators.
Here it is disadvantageous that redundant means for input, storage and readout have to be provided for each channel. Furthermore, the data to be monitored also have to be input separately by the user, redundantly for each channel.
From European Patent Disclosure EP 744 676 A2, a method and a device for safe operation of a numerical controller for machine tools or robots is known. In order to form identical output signals by means of two clock-controlled processors from identical input signals under correspondingly predeterminable conversion conditions, at the beginning of each cycle each processor, reads out its preceding output signal and the output signal of the other processor from memory means and compares them with one another. If a predeterminable deviation is found to be exceeded, error reactions are tripped. If not, a new conversion operation is performed, and the new output signals of the processors are written into the memory means.
Here it is a disadvantage that this method can be suitably employed only for process parameters newly ascertained in the course of the process. Another disadvantage is that the results of the conversion operation are compared constantly, which requires a great deal of processor capacity.
From the professional field of electronic data processing, it is known to perform cyclic redundancy checks (CRCs). In them, a checksum for a group of data is calculated by a certain algorithm. If the CRC checksums for two groups of data match, then it can be assumed with very high probability that the two groups of data are absolutely identical. This is employed for instance for bulk memories, in that a CRC checksum is additionally calculated on the basis of the data to be stored, and is stored in memory. Upon readout of the data, the CRC checksum is recalculated and compared with the stored CRC checksum. If the stored and the calculated CRC checksums match, then no error has occurred as a result of the storage in memory. If the CRC checksums differ, then an error treatment is initiated.
An object and advantage of the present invention is therefore to disclose a method in which machine parameters in a numerical controller for a machine tool are monitored for changes; essentially, the machine parameters should remain unchanged over the entire service life of the machine or controller, yet monitoring them should not require completely redundant component groups. Thus, a circuit configuration for performing the method is also to be disclosed that has as few as possible additional component groups intended especially for monitoring the machine parameters.
The above object and advantage is attained by a method for monitoring machine parameters of a numerical controller by performing a first operation of a numerical controller for machine parameters that includes calculating a first checksum of the machine parameters in a first processor, converting at least two of the machine parameters in a second processor into internal parameters of the second processor, calculating a second checksum in the second processor, transmitting the second checksum to the first processor and storing the first and second checksums in a memory. The method further entails performing a second operation of the numerical controller by calculating a third checksum of the machine parameters in the first processor, calculating a fourth checksum of the internal parameters in the second processor, comparing the stored first checksum with the calculated third checksum, comparing the stored second checksum with the calculated fourth checksum, and wherein if at least one match is lacking during the comparing, then an error treatment is performed.
The above object and advantage is attained by a method for monitoring machine parameters of a numerical controller that includes performing a setup operation of a numerical controller for machine parameters that entails storing machine parameters in a memory assigned to a first processor, calculating a first checksum of the machine parameters in the first processor, converting at least two of the machine parameters in a second processor into internal parameters of the second processor and calculating a second checksum in the second processor based on at least the internal parameters of the second processor. The method further includes transmitting the second checksum to the first processor and storing the first and second checksums in the memory.
The above object and advantage is attained by a circuit configuration for monitoring machine parameters of a numerical controller for a machine tool where the circuit configuration includes a first processor calculating a first checksum and a third checksum, a first memory assigned to the first processor and has a bidirectional connection with the first processor, wherein the first memory stores machine parameters, a second processor calculating a second checksum and a fourth checksum, a second memory that has a bidirectional connection with the first processor and the second processor and a comparator connected to the first and second memories and the first and second processors, the comparator comparing the first and third checksums with one another and the second and fourth checksums with one another.
The method of the present invention has the advantage that the embodiment of a controller with two or more channels, which is required anyway, suffices to make secure machine parameters available to all the channels of the controller. There is no need for redundant input, storage, or cyclical comparison of each individual machine parameter. This is achieved in that in the redundant channels, independent CRC checksums are calculated on the basis of the machine parameters in order to ascertain any error, and only these CRC checksums of the different channels are compared redundantly with one another.
The circuit configuration of the present invention has the advantage that already-existing component groups are used jointly for monitoring the machine parameters. Special component groups used exclusively for monitoring are unnecessary.